When to paint new plaster

Painting a newly plastered wall isn’t difficult, but there are a few more steps involved that make it different from regular painting.

Leave the plaster to dry

Plaster needs to be fully dry prior to painting. Fresh plaster can take anything from 2-6 weeks to dry fully and take on a light, uniform colour. The period of time fresh plaster needs to dry varies and is affected by the surface that has been plastered, the thickness applied, the size of the area covered, type of plaster used and of course the ambient temperature and humidity.

In most cases, 3-4 weeks is sufficient, but the best way to tell, is by checking that there are no darker spots on the plaster. A freshly-plastered wall will be a dark, uniform colour and as it dries out there will be lighter and darker areas. Wait until the whole wall is a single, light shade before painting it.

If painted before the plaster is fully dry, the paint will just trap the moisture behind a layer of paint, which will lead to problems such as damp and mould, which will cause adhesion issues which may result in flaking and peeling of the paint, creating a lot more work in the long term.

Remove imperfections

Prepare the new plaster walls by gently sanding any rough patches down first, and then move on to sealing the plaster to reduce the porous nature of the plaster. Be careful when sanding not to damage the surface, the intention is simply to remove any lumps, bumps or drips. Afterwards, use a slightly damp cloth to remove any dust. Make sure the cloth isn’t wet, the aim is not to re-wet the plaster, just simply to remove any residue on the wall.

Sealing the new plaster

Plaster is really porous so it can cause the first coat of paint to dry fairly fast, resulting in irregular brush strokes and an uneven, flaky finish. Sealing the plaster will create a base coat that is easy to paint over and will require fewer coats of paint to get a professional finish on the walls. This seal guarantees good adhesion of the top coat and vastly reduces any long term issues of peeling. Conveniently, this light, uniform colour will also show up any flaws in the plaster, so that can be addressed before adding the final colour.

There are two methods to sealing the new plaster:

  1. A primer or top coat. The first layer can be watered down by 10% which will allow the initial coat to properly soak into the plaster aiding adhesion of the second coat. Some manufacturers sell paint designed especially for use on new plaster, but these can be expensive.
  2. A mist coat paint. This is simply a watered-down general purpose water-based paint, which acts as the primer. Three parts paint to one part water is the rule of thumb. Ensures the mist is a shade lighter than the colour the wall will ultimately be painted. Never use oil or vinyl-based paints to create the mist coat, as these will not properly bind with the plaster or allow the plaster underneath to breathe.

When apply the sealer, work in smooth upward motions until the entire wall is covered. The diluted emulsion is runny so ensure drips or streaks are painted over quickly to prevent them from drying and ruining the perfect finish.

After applying the sealer, primer the walls with a plain base coat of un-watered down emulsion to provide a clean and even surface to work on. Wait 24 hours before applying the topcoat..

Painting the walls with a top coat

Once the preparation of the new plaster wall is complete, it is ready for the chosen colour of topcoat. Normally two coats of top coat are advisable to achieve the coverage required for a high quality finish. Apply one coat of paint and let it dry before applying the second coat.

And that’s it, painting new plaster really is that easy.

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